The preovulatory LH surge stimulates an increase in ovarian extracellular matrix metalloproteinase inducer (EMMPRIN), which is known as a classic regulator o fthe matrix metalloproteinases (MMPs). The paramount role of EMMPRIN in ovulation is evident from experiments in mice lacking EMMPRIN that display a decrease in oocyte release and fertilization. Yet other than our preliminary data, nothing is known as to temporal expression patterns, the regulation, and potential function of EMMPRIN in the ovulatory process in the human. This question will be addressed in the proposed POI program through a collaborative approach utilizing the exceptional backgrounds, technical expertise, and models ofthe PIs. We will make use of a unique model where the granulosa and theca from human periovulatory follicles will be collected prior to and at three designated times after hCG (early, late and postovulatory). The expression patterns of EMMPRIN in the human will be illuminated in Aim #1. Specific Aim #2 will build upon these findings to elucidate the role of EMMPRIN in ovarian angiogenesis in the human, macaque and rat. The ability of EMMPRIN to stimulate proliferation, migration and spouting of new vessels will be determined. To further characterize EMMPRIN's action. Specific Aim #3 will investigate the role of EMMPRIN in immune cell trafficking' Specifically, studies will explore the impact of EMMPRIN on leukocyte expression of the MMP system and EMMPRIN's ability to regulate the invasive capacity of leukocytes. One novel aspect of this study is the use of well characterized human preovulatory follicles as a foundation to explore the expression and function of EMMPRIN in the process of human ovulation, which has never been accomplished. Another major strength of this proposal is the collaborative interactions between different investigators to address the function of EMMPRIN in periovulatory events across multiple species. As such the proposed studies are extremely timely to elucidate the role that this exquisite proteolytic system plays in the coordinated processes of follicular rupture and oocyte release which are key aspects of normal human ovarian physiology.